Location based services require a good knowledge of the geographical position of users, outdoors as well as indoors. A user's geographical position may be determined using a Global Positioning System (GPS), or more broadly Global Navigation Satellite System (GNSS), receiver of the user's portable electronic device. Outdoors, and in areas of good GPS signal reception, the location can typically be obtained, potentially with an accuracy of approximately 5 to 10 meters.
Positioning services are often unavailable indoors, or in areas of poor GNSS signal reception. In such cases the user has to be localized via other such as assisted GPS systems that use cellular or Wi-Fi radio signal strength indicator (RSSI) measurements to provide positioning information, Wi-Fi signature analysis or radio frequency beacon system. Although these additional techniques may be helpful to provide additional location information, they typically do not provide highly accurate estimate of the location and require defined configuration.
It is desirable to provide a location technique that can provide an estimate of a location of a portable electronic device us cooperative localization techniques.